Dice have been known for many years to comprise a regular cuboid shape fabricated from a material of constant density with each of the six faces carrying one of a number (between one and six) spots. The regular shape of such dice means that they are unbiased and one of the six faces will be uppermost when the die comes to rest after having been thrown or cast by a user, the particular face being selected at random by the fall of the die.
Dice having four faces have been proposed (each face being an equilateral triangle) which have proven to be, when made properly, effective at selecting a number at random--they are unbiased.
Although attempts have been made to produce dice with more than six faces which are unbiased, these attempts have not been successful. French Patent No. 686,287 discloses a die in the form of a generally spherical body including substantially identical faces arranged in pairs having centers on ends of diameters passing through the center of the die. Thirty-eight faces are provided and are shown as concave depressions. However, those thirty-eight faces are not all evenly distributed over the otherwise spherical die body. Hence, such known dice are not essentially unbiased.
U.S. Pat. No. 3,195,895 discloses dice which are exemplary of dice formed by taking a regular polyhedron and lopping its corners to form faces having different dimensions and configurations. As a result these known dice are not free from bias. Furthermore, the angular spacings between axes defining pairs of the faces as the axes pass through the center of the die lack symmetry.